Bituminous emulsion



Jan. 17, 1933. 1 G. GABRIEL BITUMINOUS EMULSION Filed June 5, 152e e no. L o 0 n o @Woo nm@@ou en o0 ao 0% n a .Rv @o o o@ e a o .Wem Q awww.; m@ 90k@ A w @e oo .ecos M o Am. we? m. @.@Q @$0 0 a .en 0@ e@ e0 e w @e e 9 o s .8 W@ ne@ e e mwa@ e 0 e e a @e @o ww@ e mw@ @@wo@ @ou ao@ o. e. o m na@ n ou o n o G 9. @e @e o ,a m 0% 06eQ o LEONARD GOWEN GABRIEL, F LONDON, ENGLAND, ASSIGNOR, BY MESNE ASSIGN- MENTS, T0 COLAS ROADS m0., 0F BOSTON, MASSACHUSETTS, A CORPORATION 0F MASSACHUSETTS BITUMINOUS EMULSION AppliatiOn led June 5, 1928, Serial No. 283,088, and. in Great Britain May 22, 193B.

transportation and storage and on the other hand, when applied to a mineral aggregate, road surface or other foundation, t e emulsion must be capable of breaking down rapidly and yielding (by the separation of the aqueous phase) a permanent water-resistant coating of bitumen. This combination of stability and instability shall be referred to herein as the balance of stability.

The balance of stability in an emulsion is governed by the size of the dispersed bitumen particles. Generally speaking a reduction in the size of the particles means increased bulk stability but is accompaniedby a corresponding reduction in the instability factor, that is to say a reduction in the facility and speed with which the emulsion breaks when applied to a porous surface. Conversely an increase in the size of the particles diminishes the bulk stability but gives an emulsion with a quicker break on application. In emulsions which possess the required balance of stability and are now in general use the size of the greater proportifon of the bitumen particles is of the order 0 3p..

One feature of this invention resides in the manufacture of a bituminous emulsion which has the re uired balance of stability and in which a substantial proportion of the dispersed articles are of a size (e. g. 10p) considerab y greater than obtaining in the aforesaid' emulsions now generally used.

In British Specification No. 238,967 there is described a. process of making a bituminous emulsion which comprises the treatment in a colloid mill of a mixture of molten or liquid bituminous material, a proportion in the region of 1/2%2% (reckoned by weight on the bitumen) of an emulsifying agent comprising fatty acid, and a dilute aqueous solution of alkali. For example carrying out this process in a colloid mill of the rotating disc type with variable adjustable clearances using asphalt artificially produced from petroleum, introducing oleic acid (a commercial grade of pale oleine of 100% free fatty acidity) in the form of potash soap, and employmg water of hardness between 20 and 25 parts per 100,000 I have investigated the effect of variations in the proportion of the emulsier on the size of the dispersed bitumen particles in the emulsion.

As a result of these investigations I have found that for variations between 2% and 1/ 2% 1n the proportion of oleine there is practlcally no change in the average size of the particles in the emulsion. When the proport1on of oleine is carried below 0.45% there is a substantial increase in the size of the partlcles and this continues until the proportion of emulsifier is reduced below 0.36% when n o emulsiiication takes place. For proportions of emulsifier above 0.5% the average size of the bitumen particles has been found to be 3p. and the proportion of particles above 8, in diameter was exceedingly small, whileewith a proportion of 0.4% emusifier the average diameter of particles was greatly increased and the proportion of particles above 8p in diameter was considerably increased. When the proportion of emulsiiier 1s reduced to an extent (i. e. 0.45% in the particular case referred to above) such that a marked increase in the size of the bitumen particles takes place, the emulsions produced are not sufficiently stable in bulk for industrial use. I have discovered however that such emulsions may be rendered satisfactory by incorporating in them, immediately after their preparation, a stabilizing reagent.

y This invention accordingly provides a process for the manufacture of an aqueous emulsion of bitumen having the required bal ance of stability, which consists in first preparing an unstable emulsion in which the size of the greater proportion of the bitumen particles is relatively lar e, and immediately after the preparation o such emulsion incorporating therewith a stabilizing reagent. When an emulsion produced by t is process is applied say to a mineral aggregate it breaks down rapidly linto its separate constituents, and the bitumen particles being comparatively large coalesce readily to give an effective coating.

The first step in the process according to the invention consists in effecting the emulsification of bitumen with so small a propor.

E ample I 250 grams of Venezuelan asphalt at 110 C. and 125 cc. of neutral potassium oleate solution (containing the equivalent of 1 gram of oleine i. e. 0.4% oleine reckoned on the asphalt) at C. were brought togetherin a colloid mill and emulsiied thereby. The emulsion was run direct from the mill into a vessel containin 125 cc. of 0.5% elatine solution as a stabilizing reagent. Tie final product was a coarse emulsion, stable in bulk, of normal viscosity (about 0.15 dynes per square c'm.), and giving a quick break on application, accompanied by rapid reformation of the relatively large bitumen particles to produce an adhesive and cohesive film of ltumen.

' Example [I In this example another grade of Venezuelan asphalt was emplo ed. 250 grams of asphalt at 110.o C. an 125 cc. of neutral potassium oleate solution (containing the equivalent of 0.5 grams of oleine i. e. 0.2% oleine reckoned on the asphalt) at 70 C. were treated in a colloid mill, and the emulsion was run directly into a vessel containing, as before, 125`cc. of 0.5% aqueous gelatine solution. The productV was similar to that obtained in Example l.

It is to be noted that in Example Il emulsification was in the first place effected with a pro ortion of oleineas low as 0.2% reckoned y weight on the bitumen. lt will be understood that for each particular type and ade of bitumen there will be particular limits) which will vary for different t pes and grades) in the proportion of emulsi er, within which it is suitable to effect the initial emulsiflcation step according to the invention.

The accompanying drawing shows diaammatically the comparative size of the ispersed bitumen particles in an emulsion prepared by the present process.

Figure l is a representation (to a magnification of approximately 800 diameters) of a standard emulsion made by the process referred to in the opening part of this specification, that is to say carried out in a colloid mill using Venezuelan asphalt, introducing about 2% of oleic acid (reckoned by weight on -the bitumen) in the form of potash soap, and employing wat'er of the hardness hereinbefore specified. It will be noted that the proportion of particles having a diameter greater than 8.a is practically nil.

igure 2 is a representation, to the same magnification as Figure 1, of an emulsion made according to Example I. It willbe seen that the average size of the particles in this gure is considerably greater than in Figure 1. On a statistical analysis of an emulsion 4prepared according to Example I it was found that about 25% of the bitumen particles were of a diameter greater than 8p. a

It is an important feature of the emulsion produced according to the present invention, that not only does it break down quickly on application but the time interval between the break and the reformation of the bitumen as a coherent layer With its o1i ginal physical properties is very materially reduced. It is also a feature of the invention that emulsions produced accordingly posses a normal viscosity, and that the relatively coarse particles of bitumen do not lead to excessive sedimentation.

It has been found that gelatine, glue and other protein and allied substances give satisfactory results as stabilizing reagents in the present process, and a'feature of the invention resides in the use of such substances for this purpose. Other stabilizing reagents such as starch and certain other carbohydrates have also been found to give satisfactory results.

The invention is not limited to the carrying out of the process in a colloid mill, nor is it limited to the use of any particular emulsifying agent. The invention coversV bituminous materials broadly and includes within its scope the products of the processes described herein.

By the expression unstable in bulk as qualifying in the claims, the stability of an emulsion, mean to distinguish from an emullOl sion which is made with a suiiiciently large quantity of emulsifying agent to permit the `emulsion to maintain its dispersed state, i. e.7

the state in which it will not coalesce or invert spontaneously over a period of time longer than approximately three months when held in storage."

By the use of the term an inert'stabiliz- I claim:

1'. A process for the manufacture of an aqueous bituminous emulsion which comprises admixing a bitumen with an aqueous solution of such a. small quantity vof soap-like emulsifying agent as to produce an initial emulsion having relatively large particle size, bulk in stability and quick breaking characteristics, and thereafter adding an inert stabilizing agent in quantities suflicient to prevent coalescence ofthe emulsiied bitumen particles 'during storage, whereby to impart bulk stabilityto the initially formed emulsion, but in insuiiicient quantities to destroy the quickbreaking characteristics of the emulsion'when applied to a porous surface.

2. The process for the manufacture of an aqueous bituminous emulsion which comprises admixing bitumen with an aqueous solution of rsuch a small quantity of soap-like emulsifying agent as to produce an initial emulsion, in which the size of a substantial portion of the dispersed particlesis upwards of l0 mu, bulk instability and quick-breaking characteristics, and thereafter adding an inert stabilizing agent in quantities sufficient to prevent coalescence of the emulsitied bituminousy particles during storage, whereby to impart bulk stability to the initially formed emulsion but of quantities insuiiicient to destroy the quick-breaking characteristics of the emulsion when applied to a porous surface.

3. An emulsion of bitumen with water as the external phase comprising bitumen and soap-like emulsifying agent present in such a small amount as to produce an initial emulsion of relatively lar e particle size, but possessing bulk instability and quick-breaking characteristics, and an inert stabilizing agent contained in said emulsion in quantities suiicient to prevent coalescence of the emulsiiied bitumen particles during storage whereby to impart bulk stability to the. initially formed emulsion but of insufficient quantity to destroy the quick-breaking characteristics of the finalproduct when applied to a porous surface. r Y

4. An aqueous bituminous emulsion which comprises bitumen of the type artificially prepared from petroleum, water, and a proportion of soap les than 0.5%, reckoned by Weight on the bitumen, the small amount of the soap present producing an initial emulsion having a large particle size of upwards to l0 mu, quick-breaking characteristics and bulk instability, and an inert stabilizing agent present in the emulsion of a quantity insuiicient to destroy the quick-breaking characteristics of the relatively large sized bituminous particles when applied to a porous surface.

5. An emulsion of bitumen with water as the external phase comprising bitumen and a soap-like emulsifying agent present in such a small amount as to produce an initial emull sion of relatively large particle size, but possessing bulk instability and quick-breaking characteristics, and a gelatinous inert stabilizing agent contained in said emulsion in quantities suiicient to prevent coalescence of the emulsified bitumen particles during storage whereby t0 impartbulk stability to the initially formed emulsion but of insuiiicient quantity to destroy the quick-breaking characteristics of the final product when applied to a porous surface.

6. An emulsion of bitumen with water as the external phase comprising bitumen and a soap-like emulsifying agent present in such a small amount as to produce an initial emulsion of relatively large particle size, but possessing bulk instability and quick-breaking characteristics, and a carbohydrate stabilizing agent contained in said emulsion in quantities suiicient to prevent coalescence of the emulsified bitumen particles during storage whereby to impart bulk stability to the initially formed emulsion but of insulicient quantity to destroy the quick-breaking characteristics of the final product when applied to a porous surface.

In testimony whereof I aflix my signature.

LEONARD GOWEN GABRIEL. 

